1. Field of the Invention
The present invention relates generally to synthetic aperture radar. More specifically, but without limitation thereto, the present invention relates to optimization of synthetic aperture radar image formation.
2. Description of the Related Art
In monostatic synthetic aperture radar (SAR), the transmitting and receiving antennas share common hardware or a common platform. In bistatic or multistatic SAR, the transmitting and receiving antennas are distinct and at least one component can move along a path independent of the others. In military applications, a potential advantage of the data collection geometry of multistatic SAR lies in the ability of a high powered transmitter to operate at a safe distance from targeted scenes of interest while covert receivers fly closer.
Bistatic SAR is a process of generating an image by combining the magnitude and phase measurements of many spatially distributed locations of an illuminator and/or a receiver. In bistatic SAR, measurements are generally compensated for illuminator location and motion, reflective surface location, and receiver location and motion. Phase compensation is generally performed for each fast-time and slow-time sampling of the measured signals. The phase compensation coefficients can be determined accurately when the location and motion of the illuminator and receiver are accurately known. Unlike monostatic SAR where the illuminator and receiver are co-located, this information is difficult to accurately obtain in bistatic SAR making it difficult to align the two separate reference systems of a bistatic SAR system. As a result, the generation of quality images in a bistatic SAR is difficult.
Conventional bistatic and multistatic SAR imaging systems have used a data-link between the illuminator and receiver to communicate the location and motion information. This approach increases the complexity of such systems and furthermore, has several inherent difficulties and risks. For example, maintaining a data link in a real-time operational environment may be difficult due to interfering and jamming signals resulting in an inability to generate a quality image. It may also give away the location of the illuminator or receiver and may require that the receiver and illuminator be within line-of-site depending on the frequency. Thus there is a general need for an improved method and system for generating of a bistatic or multistatic SAR image.
It will be recognized that some or all of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of the elements shown. The Figures are provided for the purpose of illustrating one or more embodiments of the Optimal SAR Receiver Path algorithm with the explicit understanding that they will not be used to limit the scope or the meaning of the claims.